Sustentaculum tali in Chinese population: anatomy and clinical significance.

Background: Previous studies lacked adequate quantitative data on sustentaculum tali (ST), especially in Chinese population. The aims of this study are to explore the quantitative morphology of ST in dried bone specimens, and to discuss its implications related to ST screw fixation, talar articular facet variation, as well as subtalar coalitions.

Methods: A total of 965 dried intact calcanei from Chinese adult donors were evaluated. All linear parameters were measured by two observers with a digital sliding vernier caliper.

Results: Most parts of ST body can accommodate a commonly-used 4-mm-diameter screw, but the minimum height of anterior ST is only 4.02 mm. The shapes of the STs are slightly affected by left-right, subtalar facet, but the subtalar coalition may potentially increase the sizes of STs. The incidence of tarsal coalition is 14.09%. Among the osseous connection, there are 58.8% of type A articular surface and 76.5% of middle and posterior talar facet (MTF and PTF) involvement. ROC curve shows that subtalar coalition will be detected when ST length is greater than 16.815 mm.

Conclusions: Theoretically, all the STs can accommodate 4 mm diameter screw, but a 3.5 mm diameter screw is recommended to be placed in the middle or posterior of the small ST for safety. The shapes of the STs are greatly influenced by the subtalar coalition, while they are less affected by left-right, subtalar facet. The osseous connection is common in type A articular surface and always involved in the MTF and PTF. The cut-off value of the length of STs was confirmed as 16.815 mm for predicting subtalar coalition.